POS0906 ULTRASONOGRAPHY AND FDG-PET/CT FOR SUSPECTED POLYMYALGIA RHEUMATICA: DIAGNOSTIC PERFORMANCE IN TREATMENT-NAÏVE VERSUS ALREADY TREATED PATIENTS
Authors: K. Van der Geest, K. Bouwman, M. Sandovici, R. Slart, E. Brouwer
Journal: Annals of the Rheumatic Diseases (2023)

<h3>Background</h3> Polymyalgia rheumatica (PMR) is a common rheumatic, inflammatory disease in the elderly. Traditionally, the diagnosis is based on clinical and laboratory findings, which are not specific for PMR. Although most patients initially respond well to glucocorticoid (GC) treatment, a refractory or relapsing disease course is not uncommon and may cause doubt about the initial diagnosis. This usually prompts additional diagnostic evaluation for PMR with imaging tools such as ultrasonography and FDG-PET/CT, usually after GC tapering. However, it is unclear whether these tests perform equally well in patients already treated under the presumed diagnosis of relapsing or refractory PMR, when compared to treatment-naïve patients, suspected of new PMR. <h3>Objectives</h3> To compare the diagnostic accuracy of ultrasonography and FDG-PET/CT for PMR in treatment-naïve and already treated patients <h3>Methods</h3> Retrospective study including 144 consecutive patients that were referred to the Rheumatology and Clinical Immunology department for suspected PMR, including 63 treatment-naïve patients, and 81 already treated patients with or without still ongoing treatment. Patients were referred by general practitioners (n=107) or other medical specialist. Bilateral ultrasonographic evaluation of the shoulders and hips was performed in 135 patients. The presence of biceps tenosynovitis, subacromial bursitis, glenohumeral synovitis, hip synovitis and trochanteric bursitis was assessed. A sum score of the latter abnormalities was constructed (score range 0-10), and termed total ultrasound score. FDG-PET/CT from skull to upper legs was performed in 72 patients. FDG uptake was visually scored at 12 key sites in order to calculate the Leuven PMR-PET score (score range 0-24) [1,2]. The final clinical diagnosis at 6 months was the reference standard. <h3>Results</h3> A clinical diagnosis of PMR was made in 94/144 (65%) patients. The provisional ACR/EULAR criteria for PMR were fulfilled in 67/94 (71%) patients with PMR and in 19/50 (38%) patients without PMR. More specifically, PMR was diagnosed in 42/63 (67%) treatment-naïve patients and 52/81 (64%) already treated patients. Among the already treated patients, 24 patients were still on GC treatment during the ultrasound scan (median prednisolone dose 6.25 mg daily, range 1.25-30), while 2 patients were taking methotrexate (n=1) or leflunomide (n=1). Only 2 patients were on GC treatment during the FDG-PET/CT scan (prednisolone dose 1 and 2.5 mg), while 1 patient was treated with leflunomide. The total ultrasound score and Leuven PMR-PET score showed good diagnostic accuracy in treatment-naïve patients as indicated by the AUC in the ROC analysis (Table 1). The diagnostic accuracy of the total ultrasound score was poor in patients that had already been treated, even when GC treatment had been fully tapered. In contrast, the diagnostic accuracy of FDG-PET/CT remained good in already treated patients. <h3>Conclusion</h3> FDG-PET/CT shows equal diagnostic accuracy for already treated PMR as for treatment-naïve PMR, if GC therapy is fully tapered. However, ultrasonography for suspected PMR is best performed before initiation of treatment. A simple sum score of inflammatory lesions in the shoulders and hips aids the interpretation of ultrasonography in PMR. <h3>References</h3> [1]Henckaerts L, et al. Rheumatology 2018 Nov 1;57(11):1908-1916. [2]van der Geest KSM, et al. Rheumatology 2022 Mar 2;61(3):1072-1082. <h3>Acknowledgements:</h3> NIL. <h3>Disclosure of Interests</h3> Kornelis van der Geest Speakers bureau: Roche, Grant/research support from: AbbVie, Karin Bouwman: None declared, Maria Sandovici: None declared, Riemer Slart: None declared, Elisabeth Brouwer Speakers bureau: Roche, Consultant of: Roche.